"Kiss Me Goodbye" does not necessarily imply love. For FF12, the protagonists have lost lots of things in which they have held dear to their heart because of this war among the kingdoms.
Vaan and Penelo lost their families
Ashe losts her husband
Bache losts his glory and position as a knight

(Really, the only ones who don't appear to have lost anything because of this war are Balflear and Fran... they are pirates, what have they got to lose? Well, we'll have to buy the game to find out)

For me, "Kiss Me Goodbye" means saying farewell to the happiness these characters have had that shall never return, but they must find new happiness amidst the chaos even after much suffering because if they back down, then it really is "Kiss Me Goodbye" for good.

PS: In the PV, Ashe takes out her ring and gives it away. It could mean she's letting go of her past, trying to forget Rassler, kissing "HIM" goodbye in order to find the happiness she feels she still deserves.